Coil leads insulating and securing means



April 28, 1964 s. CALTAGIRONE COIL LEADS INSULATING AND SECURING MEANSFiled March 20, 1961 n @w g; m w 92 m% r support for the coil.

United States Patent 3,131,372 C(ltilL LEADS INSULATING AND SlECUlilNGMEANS Saverio Caltagirone, Danvilie, Iii, assignor to General ElectricCompany, a corporation of New York Filed Mar. 20, 1961, Ser. No. 97,0817 Claims. (Cl. 336-192) This invention relates to electrical coilassemblies and methods of manufacture thereof. More particularly, theinvention relates to electrical coil assemblies having windings whereinconductors are brought out from the margins of the coil assembly and tomethods of manufacture thereof.

Electrical coil assemblies generally used in transformers such asballast transformers employ one or more windings which are wound on aspool in successive layers between which insulating layers areinterposed. Where the individual winding is a filament heating winding,the individual winding may require only several turns. However, wherethe individual winding to be connected in a ballast circuit is asecondary winding, a relatively large number of turns may be required.In such a case, it is required that a conductor such as the startconductors be brought out from the coil margins to the outside wrapperof the coil in order that connections can be made to the conductor. Itis the usual practice to bring the conductor out to connectors on theoutside wrapper where the conductors can then be soldered to externalcircuit leads or other coil conductors. Because the conductor is broughtout along the margins where it can readily come in contact with thewinding itself, an adjacent coil or a magnetic shunt, it is requiredthat the conductor be provided with under insulation to insulate theunderside of the conductor from the coil assembly and over insulation toinsulate the outer side of the conductor.

Although not limited thereto, the coil assembly arrangement of thepresent invention is particularly adaptable to coil assemblies havingcoils which are multiple wound on a paper spool with paper layerinsulation interleaved between each wire layer. The paper spool servesthe double function of insulating the coil from the magnetic core of atransformer and also providing The paper insulation interleaved betweenlayers of the wire is required in order to keep each layer of wire flatand to insulate the wire layers from each other. The paper insulationalso prevents rubbing between the layers of wire. Such rubbing wouldeventually damage the wire insulation and cause a short circuit.

Electrical coils of the type described herein are generallymultiple-wound on a continuous spool. After the winding operation iscompleted, a wrapper is applied on the top of the last layer of wire andsaw marks are made on the strip to indicate the point at which theindividual coils are to be sliced. After the individual coils aresliced, the start and finish conductors are pulled out of the margin andfinished off. Since the finishing operation is done by hand, it isdesirable that the conductors be finished ofl quickly and easily. Thefinishing operation includes the application of over and underinsulation for certain conductors.

A common method used in the past required the application of twosubstantially rectangular shaped gummed insulating pieces of paper to aconductor to insulate it. According to this method of assembly, thefirst piece was wetted on its gurnmed side and placed into the margin ofthe coil in front of the coil conductor. It was then bent over themargin and glued to the coil body. A second insulating piece was placedinto the coil margin over the first piece and over the conductor. It wasbent over the first piece and [glued to it in order to provide the overinsulation for the conductor and firmly position the coil conductor. Oneof the disadvantages of this prior art method was that it required thattwo separate insulating pieces be applied in order to provide over andunder insulation for a coil conductor. One of the difficultiesencountered with the two insulating piece arrangement was that the outerinsulating piece often worked loose or became sufficiently loose topermit the coil conductor to slip out. There is a need, therefore, for aconductor insulating arrangement wherein the over and under insulationcan be readily'applied and wherein the coil conductor can be effectivelyretained .in place and insulated.

Accordingly, it is the general object of the present invention toprovide a core assembly having an improved means for insulating theconductors brought out from a coil.

it is another object of the invention to provide a coil assembly thatcan be readily assembled and that utilizes a minimum number of pieces.

A more specific objection of the invention is to provide an improvedcoil assembly having an improved conductor insulating and securing meanswhereby a conductor brought out from the coil is effectively insulated.

Another object of the invention is to provide an improved method forapplying over and under insulation for coil conductors brought out froma coil.

in one form of the invention 1 have provided an electrical coil assemblycomprising a winding formed of plurality of wire layers and insulatinglayers interleaved therebetween, the winding having at least a start.conductor and a finish conductor. An insulating tab is provided for atleast one of said conductors and it is formed with a pair of attachingportions and over an under insulating portions. The under insulatingportion is folded under the conductor and attached to the overinsulating portion so the conductor is firmly engaged between theinsulating portions.

One of the attaching portions is secured to the coil underside and theother attaching portion is secured to the coil wrapper or other portionof the coil where the conductor is to be connected in circuit.Preferably, the coil conductor is positioned in the corner fold formedby folding the under insulating portion under the over insulatingportion.

According to the method of the present invention, the under insulatingportion of the insulating tab is folded over a coil conductor and gluedto the over insulating portion of the insulating tab so that the coilconductor is firmly secured between the over and under insulatingportions and is brought out at the corner fold of the under insulatingportion of the tab so that the coil conductor is retained in position bythe corner fold and the glued surfaces of the under and over insulatingportions.

The subject matter which I regard as my invention is particularlypointed out and distinctly claimed in the concluding portion of thisspecification. My invention, however, both as to organization and methodof opera tion, together with further objects and advantages thereof, maybest be understood by reference to the following description taken inconjunction with the accompanying drawings in which:

PEG. 1 is a partially sectionalized view of a coil assembly with aportion of the spool cut away to show the start anchor strip and a coilconductor brought out from the under side of the coil;

FIG. 2 is a view of the coil assembly corresponding to the view shown inFIG. 1 in which the insulating tab is shown in position prior toassembly with the under insulating portion partially folded over;

FIG. 3 is a perspective view of the insulating tab partially folded overshowing the gummed underside of the insulating tab;

FIG. 4 is another sectionalized view of the coil assembly wherein aportion of a spool is cut away to show the insulating tab in assembledrelation with the coil assembly;

FIG. 5 is a sectionalized view taken along line 5--5 of the coilassembly shown in FIG. 4;

FIG. 6 is a perspective view of the coil assembly in accordance with theinvention showing the insulating tab in assembled relation with the coilassembly and having a part of the coil wrapper cut away to show thefinish conductor anchor strip;

FIG. 7 is a fragmentary view of the back side of the coil assembly shownin FIG. 6 illustrating the manner in which the insulating tab isattached to the coil wrapper and the start conductor is engaged by thefold formed by the over and under insulating portions; and

FIG. 8 illustrates a continuous gumrned strip from which the insulatingtabs may be cut without scrap.

Referring now to the drawing, I have illustrated therein an electricalcoil assembly 9 having winding formed of a plurality of wire layers 12wound on a spool 15 Interleaved between the wire layers are a pluralityof insulating layers 13. The insulating layers 13-5 are interposedbetween the wire layers 12 so that movement between adjacent wire layers12 will not cause wear of the Wire insulation and cause short circuitsto occur in the coil.

In the embodiment of the invention illustrated in the drawings, the coilassembly 9 is provided with a start conductor 14 and a finish conductor15, which are held in position by anchor strips 16, 17. Anchor strips16, 17 are provided so that the coil conductors 14, 15 brought out fromthe coil assembly 14) are firmly secured to the coil assembly and sothat a conductor layer is not pulled out as tension is applied toconductors 14, 15.

The anchor strip 16 for the start conductor 14 is best seen in the viewsof the coil assembly 9 shown in FIGS. 1 and 2 while the finish anchorstrip 17 for the finish conductor 15 is best seen in the view shown inFIG. 6. In FIG. 1 anchor strip 16 is shown in imaginary outlinewithdrawn from coil assembly 9 where it is interposed between the spooland lowermost wire layer 12.

Although preferably the coil conductors 14, are anchored in position oncoil assembly a by the use of anchor strips 16, 17, it will beappreciated that the coil conductors 14, 15 may be anchored by othersuitable means such as by securing the coil conductor to the coil layerby cloth adhesive tape as is frequently done in the manufacture ofelectrical coils. Anchor strips are preferably employed since rnoreuniform radial dimensions of the coil can be maintained. Cloth anchortape frequently bunches up during assembly and thereby introduces a highspot. An advantage achieved by the use of an anchor strip is that thestart and finish conductors of a coil assembly may be more accuratelypositioned. As shown in FIG. 1, when the coil conductor 14 is pulled outand caught in the conductor positioning slot 11 provided in the anchorstrip, it is precisely positioned at a fixed axial distance from the endof the coil assembly 9.

Layer insulation is continuously wound with wire layers 12; so that theinsulation layers 13 are interleaved between wire layers 12. Preferably,the layer insulation may be formed of thin paper since it has gooddielectric properties and is a relatively inexpensive material. Thespool 10 may also be formed of paper and with a rectangular opening thatconforms to the cross sectional configuration of the magnetic core leg(not shown) on which the coil assembly 9 will be mounted. Thus, thespool 10 disposed at the underside of the coil assembly 9 serves thepurpose of insulating the wire layers 12 from the magnetic core and alsoserves 'as a support member for the coil assembly 9. An outer wrapper18, preferably of kraft paper, is provided over the outer wire layer andserves as a protective covering for the coil assembly 9.

It will be understood that during manufacture a plurality of windingsare wound at one time on a continuous spool which is mounted on anarbor. Wherever a conductor is to be brought out from the coil, acontinuous anchor strip having a plurality of anchor slots is positionedso that the wires are engaged in individual slots. A few turns of wireare wound on the spool, and these additional turns provide the amount oflead required for a particular conductor. The outer Wrapper is thenapplied on the spool and the entire spool is sliced into individualcoils. After the slicing operation is completed, individual conductorsare pulled out. Thus, the coil assembly 9 shown in FIG. 1 represents anindividual coil that has been sliced off and is ready for the conductorfinishing operation and assembly in accordance with the invention.

Referring now to FIG. 2, it will be seen that an insulating tab 19 isshown in partially assembled relation with the coil assembly 9. Theinsulating tab 19 is formed with an upper attaching portion 29, a lowerattaching portion 21, an over insulating portion 22 and an underinsulating portion fiap 23. One side of the insulating tab is gummed, sothat it can be made to readily adhere to the coil assembly h, as isshown in FIG. 3.

In the illustrative embodiment of the invention, I have employed a lowerattaching portion 21 which is slightly shorter in length than the upperattaching portion 20. As shown in FIG. 2 the lower attaching portion 21is inserted between the coil underside and the coil spool 10 so that thegummed side of attaching portion 21 adheres to the coil underside. Ifdesired, the attaching portions 20, 21 may be substantially equal inlength.

In FIGS. 4, 5, 6 and 7, I have shown the insulating tab 19 in finalassembled relation with the coil assembly 9. it will be seen that theattaching portion 21 of insulating tab l9 is inserted between the spool19 and the anchor strip 16 so that the gummed side of attaching portion21 adheres to the anchor strip 16. Attaching portion 2t) is bent overand the glued underside adheres to the coil wrapper 18. Having morespecific reference to the cross sectional view of the portion of thecoil assembly 9 shown in FIG. 5, it will be noted that the underinsulating portion 22 is interposed between the conductor 14 and thewire layers 12. The under insulating portion 23 is folded under the overinsulating portion 22 and start conductor 14 is securely sandwichedbetween the glued surfaces of the over insulating portion 22 and underinsulating portion 23.

Heretofore, over and under insulation for a coil conductor was providedby using two substantially rectangular shaped gumrned pieces. The firstgummed piece was attached at one end to the underside of the coil, thecoil side and at the other end to the coil wrapper. This first pieceprovided the under insulation for the coil conductor. The conductor wasplaced over the first piece. The second gummed strip was then placedover the conductor and glued to the first piece. The arrangementaccording to the present invention provides very significant advantagesover such prior art methods of manufacture. In accordance with theinsulating tab arrangement of the invention, the insulating tab 19 issecurely attached to coil assembly 9 in a one step finishing o e ation.The under insulating portion 23 is simply folded over the coil conductor14 as shown in FIG. 2. The lower attaching portion 21 is insertedbetween the coil underside and coil spool 10 with the gummed side facingthe coil underside to which it attaches. The upper attaching portion 20is bent over with the gummed side overlying the coil wrapper 18. Thus,the gummed side of the attaching portion 2% adheres to the coil wrapper18. Therefore, it is only necessary to handle a single piece in themanual assembly operation and the finishing operation can beaccomplished by simple manipulation of the insulating tab 19. Further,the arrangement of the invention provides the advantage that the underinsulating portion 23 is integrally a part of the over insulatingportion 22 and the coil conductor 14 is thereby securely positionedbetween two glued surfaces.

In many applications, the wire used for a coil winding is oftenhair-thin in size. Where separate insulating pieces are used to provideover and under insulation for a coil conductor, the hair-thin wire maycause the glued pieces to separate as tension is applied to theconductor due to the shearing action of the wire. As is best seen in theview shown in FIG. 7, the start conductor 14 is preferably brought outso that it engages the corner fold that is formed when the underinsulating portion 23 is folded under the start conductor 14. With thisarrangement, start conductor 14 is firmly secured and tension applied tothe coil conductor 14 will not readily cause the glued portions of theinsulating tab 19 to separate since conductor 14 is engaged against thecorner fold.

Since outer and inner insulating portions 22, 23 are glued together bytwo gummed surfaces, it will be apparent that where two gummed surfacesare joined, the surfaces are less likely to separate than where onegummed surface is joined to another which is not glued. Thus, even ifthe attaching portions 22, 23 of the insulating tab 19 separate from thecoil assembly 9, the conductor 14 is still retained in position betweenthe over and under insulating portions 22, 23.

It will be understood that while I have illustrated my invention by aspecific embodiment thereof, many modifications rnay be made by thoseskilled in the art without departing from the invention. T bus, theconfiguration of the insulating tab and the manner of attachment to thecoil assembly may be varied. It is, therefore, intended in the appendedclaims to cover all such appended claims to cover all such equivalentvariations that face within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrical coil assembly comprising a winding formed of aplurality of wire layers, a plurality of insulating layers interposedbetween said wire layers, at least one coil conductor brought out fromone of said wire layers, means for anchoring said coil conductor to saidcoil assembly, a coil Wrapper encompassing the outer wire layer andproviding an insulating and protective covering for said layer, and aninsulating tab having one gummed side and having a pair of attachingportions and over and under insulating portions, one of said attachingportions securing said insulating tab at said gummed side to the coilunderside and the other of said attaching portions securing theinsulating tab at said gummed side to the coil wrapper, said underinsulating portion providing insulation between said coil conductor andsaid winding and said over insulating portion providing insulation forthe outer side of saidcoil conductor, said under insulating portionbeing integrally formed with said over insulating portion and beindfolded over under said coil conductor to engage the coil conductortherebetween and securely position the coil conductor on the coilwrapper.

*2. The electrical coil assembly as set forth in claim 1, wherein thecoil conductor is positioned against the corner fold formed by the underand over insulating portions of said insulating tab.

3. In an electrical coil assembly formed of a plurality of wire layershaving insulating layers interleaved theretom wire layer of said coilassembly to the outer portion thereof, an insulating tab having one sidecompletely gummed, an over insulating portion folded over said coilconductor and an under insulating portion folded under said conductorand attached to said over insulating portion at the gummed side thereof,said insulating tab having between and a start conductor brought outfrom the bota pair of attaching portions one of said attaching portionsbeing secured at the gummed side to the coil underside and the otherattaching portion being secured at the gummed side to an outer portionof said coil assembly.

4. An electrical coil assembly comprising a spool, a winding wound in aplurality of wire layers on said spool, a plurality of insulating layersinterleaved between said wire layers, a start anchor strip disposedbetween said spool and a wire layer, said anchor strip being formed witha conductor positioning slot, a coil conductor engaged in said conductorpositioning slot of the anchor strip and brought out from said windingto provide a terminal connection for said winding, an insulating tabhaving a pair of attaching portions, one of said attaching portionsbeing connected to said anchor strip and the other of said attachingportions being connected to an outer portion of said coil assembly, saidinsulating tab having an under insulating portion folded under the coilconductor so as to provide insulation between the coil conductor and thewinding, and said insulating tab having an over insulating portionfolded under the coil conductor and attached to said over insulatingportion to securely engage said coil conductor and to insulate the outerside thereof.

5. The electrical coil assembly as set forth in claim 4 wherein the coilconductor is positioned against the corner fold formed by the under andover insulating portions of said insulating tab.

6. An electrical coil assembly comprising a spool, a winding wound in aplurality of wire layers on said spool, a coil wrapper encompassing theouter wire layer and provide an insulating and protective covering forsaid layer, at least one coil conductor brought out from said winding toprovide a terminal connection for said winding and an insulating tabhaving one gummed side and having a pair of attaching portions, one ofsaid attaching portions being attached at said gummed side within thecoil and the other of said attaching portions being attached at saidgummed side to said coil wrapper of said coil assembly, said insulatingtab having an under insulating portion folded under the coil conductorso as to provide insulation between the coil conductor and the winding,and having an over insulating portion folded over the coil conductor andjoined to the gummed side of said under insulating portion therebyinsulating the outer side of said conductor.

7. The electrical coil assembly as set forth in claim 6, wherein thecoil conductor is positioned against the corner fold formed by the underand over insulating portions of said insulating tab.

References Cited in the file of this patent UNITED STATES PATENTS1,752,866 Trombetta Apr. 1, 1930 2,122,894 Sager July 5, 1938 2,159,269Hasse May 23, 1939 2,264,832 Ensign Dec. 2, 1941

3. IN AN ELECTRICAL COIL ASSEMBLY FORMED OF A PLURALITY OF WIRE LAYERSHAVING INSULATING LAYERS INTERLEAVED THERETOM WIRE LAYER OF SAID COILASSEMBLY TO THE OUTER PORTION THEREOF, AN INSULATING TAB HAVING ONE SIDECOMPLETELY GUMMED, AN OVER INSULATING PORTION FOLDED OVER SAID COILCONDUCTOR AND AN UNDER INSULATING PORTION FOLDED UNDER SAID CONDUCTORAND ATTACHED TO SAID OVER INSULATING PORTION AT THE GUMMED SIDE THEREOF,SAID INSULATING TAB HAVING BETWEEN AND A START CONDUCTOR BROUGHT OUTFROM THE BOTA PAIR OF ATTACHING PORTIONS ONE OF SAID ATTACHING PORTIONSBEING SECURED AT THE GUMMED SIDE TO THE COIL UNDERSIDE AND THE OTHERATTACHING PORTION BEING SECURED AT THE GUMMED SIDE TO AN OUTER PORTIONOF SAID COIL ASSEMBLY.